Finishing a surface of a substrate often includes three steps: grinding, lapping and polishing. A grinding process can be used to create a rough form of the substrate, to reduce the substrate to a desired size, and/or remove large defects on the substrate surface. The grinding process generally has a relatively high material removal rate, often causes sub-surface damage to the substrate, and can leave a relatively rough surface finish on the substrate. Lapping is an intermediate finishing step that has a lower material removal rate than grinding and generally causes less sub-surface damage. The lapping process generally produces a relatively smooth surface. Finally, the polishing process has the lowest material removal rate and is generally used to provide smooth substrate surfaces often having defects less than about four microns in size, which are generally not visible to the naked eye.
When lapping hard surfaces, such as sapphire and the like, the lapping process often includes placing the substrate in a carrier and moving the substrate surface(s) relative to a lapping medium or lapping media in the presence of a slurry. The lapping media often include a soft metal plate, such as a copper plate, having patterned grooves formed into a surface of the plate. The slurry includes abrasive particles, such as diamonds in a carrier liquid. The lapping plate provides a hard surface for the abrasive particles to roll along as the substrate surface is moved relative to the lapping medium. Material is removed from the substrate surface using relative movement of the media and the substrate, which causes the abrasive particles roll or move. As the abrasive particles move, the particles scratch and/or puncture part of the substrate surface, causing small pieces of the substrate surface to be removed.
Typical metal plates are relatively large (e.g., having a diameter of about forty inches) and relatively thick (e.g., having a thickness of about one inch), making the plates heavy (e.g., about 150 pounds). Use of the large, heavy plates as lapping media may be desirable because the large metal plates can be used to lap large surfaces or a plurality of surfaces and the thickness of the metal plates helps the plates maintain their flatness and parallelism—e.g., parallel with respect to another plate or a platen.
During use, the metal lapping plates tend to wear due to abrasion from the abrasive particles in the slurry. The wear can result in reducing flatness and/or parallelism of the metal plates, which in turn can result lower uniformity of material removal rates across the substrate surface or even situations that cause the substrates to come out of the carrier. Additionally or alternatively, the grooves in the metal plate wear (decreases in depth) during use. Accordingly, the metal plates are periodically machined to restore desired flatness, parallelism, and/or groves/groove depth. If the plate is not thick enough to reform the grooves, then a plate can be replaced with a thicker plate including grooves of the desired depth.
The machining process can be relatively expensive and time consuming. During the machining process, the plates are removed from the lapping system, the plates are ground to a desired flatness and/or parallelism and/or grooves are formed within the plates, and then the plates are reattached to the lapping system. All of these steps take considerable time and effort, which adds to a cost of lapping or finishing a surface of a substrate.
Accordingly, improved lapping materials, media, apparatus, and systems including improved lapping materials, as well as methods of forming and using the materials, media, apparatus, and systems are desired.